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["Davanum Srinivas \(DIMS\)" <davanum@xxxxxxxxx>]

for keystone :)

** Changed in: keystone
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1549516

Title:
  Too many reconnections to the SQLalchemy engine

Status in OpenStack Identity (keystone):
  Invalid
Status in oslo.db:
  New

Bug description:
  === Issue Description ===

  It looks like for every DB request oslo.db is reconnecting to the
  SQLalchemy engine, that leads to  "SELECT 1" request to the database
  per every meaningful request.

  === Prelude(<DinaBelova>) ===

  I was testing osprofiler library (OpenStack profiler) changes, that
  are currently on review for Nova, Neutron and Keystone + OSprofiler
  integration, trying to perform nova-boot requests. After generating
  the trace for this request, I got the following html report:
  https://dinabelova.github.io/nova-boot-keystone-cache-turn-on.html .
  Total number of DB operations done for this request is 417, that seems
  too much for the instance creation. Half of these requests is "SELECT
  1" requests, that are used by oslo.db per engine connection via
  _connect_ping_listener function -
  https://github.com/openstack/oslo.db/blob/master/oslo_db/sqlalchemy/engines.py#L53

  I ensured that all of these requests are coming from this method via
  adding _connect_ping_listener tracing https://dinabelova.github.io
  /nova-boot-oslodb-ping-listener-profiled.html - so we can see that all
  "SELECT 1" requests are placed under db_ping_listener section in the
  trace.

  These "SELECT 1"s are in fact spending 1/3 of all time SQLalchemy
  engine in oslo.db is spending on all requests. This seems to be a bug.

  === Env description & spets to reproduce ===

  I have devstack environment with latest 1.1.0 osprofiler installed. To
  install profiler on the devstack env I used the following additions to
  the local.conf:

  enable_plugin ceilometer https://git.openstack.org/openstack/ceilometer master
  enable_plugin osprofiler https://git.openstack.org/openstack/osprofiler master

  Additionally I've used the following changes:
  - Nova: https://review.openstack.org/254703
  - Nova client: https://review.openstack.org/#/c/254699/
  - Neutron: https://review.openstack.org/273951
  - Neutron client: https://review.openstack.org/281508
  - Keystone: https://review.openstack.org/103368

  Also I've modified standard keystone.conf to turn memcache caching:

  [cache]

  memcache_servers = 127.0.0.1:11211
  backend = oslo_cache.memcache_pool
  enabled = True

  Then you can simply run nova --profile SECRET_KEY boot --image
  <image_id> --flavor 42 vm1 to generate all notifications and then
  osprofiler trace show --html <trace_id> --out nova-boot.html using the
  trace id printed in the bottom of nova boot output.

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